<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>引用方式</title>
</head>
<body>
<!-- js写在元素上 -->
<button onclick="alert('hello world')">点击</button>
<!-- 内部调用 -->
<script>
    //单行注释
    /*
     多行注释
    */
    console.log('内部引用')
</script>
<!-- 外部调用 -->
<script src="./js/test01.js"></script>
</body>
</html>